1. Field of the Invention
The subject invention relates to calendars, including perpetual and multi-year calendars, calendar design and calendar construction.
2. Description of the Prior Art
The present Gregorian calendar, widely used throughout the Occident, is characterized by constant monthly changes either in the day-of-the-week start of a month or its length, or both. Successive years do not begin on the same day of the week. To keep up with these changes, new calendars are printed every year, which become useless and are discarded at the end of the particular year.
Perpetual and multi-year calendars are designed to display the calendar of each month of the year, year after year, utilizing the same two sets of imprinted calendar data. The pair of data components used for display are calendar data comprising indications of the days of the week by name and calendar data comprising indications of the days of the month by number. Since these two calendar data sets have a constantly changing relationship to each other from month to month (except from February to March in a common year), they are put on separate panels or other means, one of which is made movable relative to the other which is typically kept stationary. There are seven positions of the movable means relative to the stationary means, representing the seven possible relationships between the two calendar data sets with the beginning of a month on each of the seven days of the week.
Calendar setting has to do with the positioning of the movable means bearing one set of calendar data relative to the stationary means bearing the other set of calendar data so that the columns of the days of the week by name and the numbers of the days of the month are properly aligned to display the calendar for a particular month of the year.
Prior-art proposals in this area have made various attempts at teaching the user where to position the mentioned movable means relative to the stationary means.
In a first group of prior-art proposals are calendars in which information on calendar setting is obtained from prepared tables and charts attached to the calendars. It is a simple matter to construct "perpetual calendar" charts and tables covering periods of decades and centuries. Such tables are attached to the calendars of Wynne, U.S. Pat. No. 1,275,350, and Mayhew, U.S. Pat. No. 2,397,877, for reference by the user. A Pennygraf slide chart calendar (Pennygraf Division of Nashua Corporation of Los Angeles, Calif.) also belongs in this category although it is designed for only a short period (e.g. 1970-75).
In a second group of prior art proposals are calendars in which the only information supplied are the lengths of the months. From the current setting of the calendar, information as to the length of the current month can be used by the user to determine the day-of-the-week start of the following month and to reset the calendar accordingly.
This method suffers disadvantages in that the displays of the monthly calendars can be shown only in sequence and there is no correlation between the month for which the calendar is set and the displayed other calendar data. A prior-art calendar marked "Mormon Temple, Salt Lake City" is an example of a calendar in this class. Briefly, that prior-art calendar has the months and their respective lengths listed on a wheel which is rotatable relative to a window through which the name of one month at a time and the number of its days are visible. The days of the month are contained in a thirteen-column set on an endless tape which is movable relative to a stationary set of days of the week by name.
In the prior art are the calendars on the commercially available calendar wrist watches by Longines-Wittnauer Watch Company and by Neuvex, and the circular pocket calendar of Anderson & Sons, Inc. of Westfield, Mass. Briefly, these calendars have the days of the week by name listed in a first circular array on a disc, and a number of years in a second circular array on that disc. The days of the week listings are visible through a first elongate window relative to a stationary seven-column list of days of the month. The year listings are visible through a second elongate window relative to a seven-column stationary list of the months by name. Leap years are handled by special listings of January and February. Also in this category is the calendar of Lauer, U.S. Pat. No. 1,558,020.
Zabriskie's calendar, U.S. Pat. No. 1,073,206 has the semblance of belonging to the last group in that it uses an index and calendar data comprising indications of the months of the year in calendar setting, but like the calendars of the above mentioned first group, it also has a table of years for reference in selecting the index for the year.
The calendar data comprising indications of the months of the year are not simply a listing of the months of the year in sequence. Starting with the indication of January, the indication of each successive month is put down successively in selected columns of a seven-column scale according to the length of the previous month. The resultant distribution shows the indications of the months of the year arranged according to their day-of-the-week beginnings relative to that of January and, therefore, relative to each other's.
In some prior-art calendars, calendar data comprising indications of the months of the year include additional and separate indications of January and February to be used only in a leap year.
Some prior-art proposals include an index feature intended to facilitate setting. In Lauer, U.S. Pat. No. 1,558,020 the index is the 1-column (column comprising the numbers 1, 8, 15, 22, 29) in the indications of the days of the month by number.
In Zabriskie, U.S. Pat. No. 1,073,206, the index is one of the alphabetically keyed positions. In the calendars on the Neuvex and Longines-Wittnauer wrist watches and the circular calendar of Anderson & Sons, Inc., the index is the indication of the year included in the calendar data comprising indications of the years by number.
The position of the index relative to the calendar data comprising indications of the months of the year which is good in setting the calendars of the months of the year in a particular year will not be good for the following year. For the calendar setting procedure to be operative each year, the position of the index can be changed each year. This introduces the problem of determining the index position for each new year. It is the manner in which this is done which determines the nature of the calendars.
In the calendars on the Neuvex and Longines-Wittnauer wrist watches and the circular pocket calendar of Anderson & Sons, Inc., the indication of the year marks the index position for the year and the indication of the following year in an adjacent or next to an adjacent position represents the adjustment in index position for the following year as well as the index position for the following year. Since the new positions of the index for each year are predetermined and pre-labeled with the indications of the years, the life or duration of usefulness of a calendar is limited to the indications of the years contained in the particular calendar. These calendars which include indications of the years have a beginning and an end and are, therefore, at best multi-year, but not perpetual calendars.
It is axiomatic that a calendar in this group to be operated perpetually cannot have the new index positions for the years pre-determined and pre-labeled. This information must be self-generated to obtain continuous operation of the calendar.
The calendar of Ball et al, U.S. Pat. No. 786,618, is an annular calendar displaying all twelve monthly calendars at a time. In operation, it is similar to the monthly calendars in the above mentioned group having an indexing feature, in that the twelve monthly calendars are set (at one time) by aligning an index with an indication of the year included in calendar data comprising indications of the years by number. However, the calendar data comprising indications of the years in the calendar of Ball et al are more akin to the calendar data comprising indications of the months of the year than to the calendar data comprising indications of the years found in the calendars on the above mentioned wrist watches, because these calendar data (e.g. Ball et al) do not have any indexing function for the months.
The calendar by Leckey, U.S. Pat. No. 1,266,499, serves only the purpose of display, while Davis' perpetual calendar machine, U.S. Pat. No. 3,443,331, is immensely mechanically complex.